Chapter 17: From Gene to Protein Flashcards
Terms : Hide Images [1]
| 667155687 | Gene Expression | -the DNA-directed synthesis of proteins (or RNAs), includes two stages, called transcription and translation | |
| 667155688 | A. Garrod | -first suggested that genes determine phenotype through the action of enzymes, reasoning that inherited disease were caused by an inability to make certain enzymes | |
| 667155689 | G. Beadle and E. Tatum's Experiment | -worked with mutants of a bread mold, Neurospora crassa, in order to demonstrate the relationship between genes and enzymes -did this by growing nutritional mutants on complete growth medium and then transferring samples to various combinations of minimal medium and one added nutrient -they were able to identify the specific metabolic defect for each mutant -From the growth patterns of the mutants, they deduced that each mutant was unable to carry out one step in the pathway for synthesizing arginine, presumably because it lacked the necessary enzyme -Because each of their mutants was mutated in a single gene, they concluded that each mutated gene must normally dictate the production of one enzyme -Their results supported the one gene-one enzyme hypothesis and also confirmed the arginine pathyway | |
| 667155690 | Difference between RNA and DNA | (1) The sugar component of its nucleotides is ribose, rather than deoxyribose (2) Uracil (U) replaces thymine as one of its nitrogenous bases (3) Usually single stranded | |
| 667155691 | Transcription | -the synthesis of RNA on a DNA template -the transfer of information from DNA to messenger RNA (mRNA) or another type of RNA, using the "language" of nucleic acids -making mRNA -synthesis of complementary RNA strand -RNA polymerase | |
| 667155692 | Messenger RNA (mRNA) | -a type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein -carries information specifying amino acid sequences of proteins from DNA to ribosomes | |
| 667155693 | Translation | -the synthesis of a polypeptide using the genetic information encoded in an mRNA molecule -there is a change in "language" from nucleotides to amino acids | |
| 667155694 | Ribosomes | -the sites of translation-the synthesis of a polypeptide -a cell organelle constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm; consists of rRNA and protein molecules, which make up two subunits -facilitate the specific pairing of tRNA anticodons with mRNA codons during protein synthesis -all are identical, whether they are free ribosomes that synthesize cytosolic proteins or ER-bound that make membrane and secretory proteins | |
| 667757711 | RNA Processing | -modification of RNA before it leaves the nucleus, a process unique to eukaryotes | |
| 667757712 | Primary Transcript | -an initial RNA transcript; also called pre-mRNA when transcribed from a protein-coding gene -serves as a precursor to mRNA, rRNA, or tRNA, before being processed by splicing or cleavage -some intron RNA acts as a ribozyme, catalyzing its own splicing | |
| 667757713 | Triplet Code | -a set of three-nucleotide-long words that specify the amino acids for polypeptide chains | |
| 667757714 | Template Strand | -the DNA strand that provides the template for ordering the sequence of nucleotides in an RNA transcript -transcribed DNA strand | |
| 671031763 | Coding Strand | -untranscribed DNA strand -same sequence as RNA | |
| 667757715 | Codons | -a three-nucleotide sequence of DNA or mRNA that specifies a articular amino acid or termination signal; the basic unit of the genetic code -read in the 5' to 3' direction | |
| 667757716 | Reading Frame | -the way a cell's mRNA-translating machinery groups the mRNA nucleotides into codons -the nucleotide sequence on mRNA is read starting at a start codon and reading each triplet sequentially | |
| 667757717 | Promoter | -a specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing DNA | |
| 667757718 | RNA polymerase | -an enzyme that links together the growing chain of ribonucleotides during transcription -untwists the double helix, exposing DNA nucleotides for base pairing with RNA nucleotides, and joins the nucleotides to the 3' end of the growing polymer | |
| 667757719 | Terminator | -in prokaryotes, a special sequence of nucleotides in DNA that marks the end on a gene -it signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene | |
| 667757720 | Transcription Unit | -a region of a DNA molecule that is transcribed into a an RNA molecule | |
| 667757721 | TATA Box | -a promoter DNA sequence crucial in forming the transcription initiation complex | |
| 667757722 | Transcription Factors | -regulatory proteins that bind to DNA and stimulates transcription of specific genes -bind to promoter region -suite of proteins which bind to DNA -turn on or ff transcription -trigger the binding of RNA polymerase to DNA | |
| 667757723 | Transcription Initiation Complex | -the completed assembly of transcription factors and RNA polymerase bound to the promoter | |
| 667757724 | Poly-A tail | -the modified end of the 3' end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides | |
| 667757725 | 5' cap | -the 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide | |
| 667879719 | Intron | -a noncoding intervening sequence within a eukaryotic gene -some are involved in regulating gene activity, and splicing is necessary for the export of mRNA from the nucleus -may facilitate recombination of exons between different alleles or even between different genes | |
| 667879720 | Exons | -a coding region of a eukaryotic gene -are separated from each other by introns -expressed in protein synthesis | |
| 667879721 | RNA Splicing | -the removal of noncoding proteins (introns) of the RNA molecule after initial synthesis | |
| 668284307 | snRNP | -small nuclear ribonucleoproteins | |
| 668284308 | snRNA (Small Nuclear RNA) | -small nuclear RNA -function may be catalytic in intron removal -plays structural and catalytic roles in spliceosomes, the complexes of protein and RNA that splice pre-mRNA | |
| 668284309 | Splicesome | -a complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron and joining the two adjacent exons -snips an intron out of the RNA transcript and connects the adjoining exons | |
| 668284310 | Ribozymes | -RNA molecules that act as enzymes | |
| 668284311 | Properties of RNA that allows them to function as enzymes | (1) It is single-stranded and can base-pair with itself, forming a specific three-dimensional structure (2) Some of its bases contain functional groups that can participate in catalysis (3) It can hydrogen-bond with other nucleic acid molecules, allowing it to precisely locate slicing regions | |
| 668284312 | Alternative RNA Splicing | -allows some genes to produce different polypeptides -a type of regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns | |
| 668284313 | Domains | -functional segments of a protein -an independently folding part of a protein | |
| 668284314 | Exon Shuffling | -introns may facilitate recombination of exons between different alleles or even between different genes which can result in novel proteins | |
| 669180906 | Transfer RNA (tRNA) | -an RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA -serves as adapter molecule in protein synthesis; translates mRNA codons into amino acids | |
| 669180907 | Anticodon | -a specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule, thus assuring that amino acids are arranged in the sequence prescribed by the transcription of DNA | |
| 669180908 | Aminoacyl-tRNA Synthetase | -an enzyme that joins each amino acid to the correct tRNA to create an aminoacyl tRNA -hydrolysis of ATP drives this process | |
| 669180909 | Wobble | -a violation of the base-pairing rules in that the third nucleotide (5' end) of a tRNA anitcodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon -thus, one tRNA can recognize more than one mRNA codon, all of which code for the same amino acid carried by that tRNA | |
| 669180910 | Ribosomal RNA (rRNA) | -the most abundant type of RNA, which together with proteins forms the structure of ribosomes -ribosomes coordinate the sequential coupling tRNA molecules to mRNA codons -plays catalytic (ribozyme) roles and structural roles in ribosomes | |
| 669180911 | What are the three stages of protein synthesis? | (1) Initiation (2) Elongation (3) Termination | |
| 669180912 | Initiation Stage of Translation | 1) A small ribosomal subunit binds to both mRNA and a specific initiator tRNA, which carries the amino acid methionine 2) The small subunit then moves, or scans, downstreamalong the mRNA until it reaches the start codon, AUG, which signals the start of translation; this is important because it establishes the codon reading frame for the mRNA 3) The initiator tRNA, already associated with the complex, then hydrogen bonds with the start codon. 4) The union of mRNA, initiator tRNA, and a small ribosomal subunit is followed by the attachment of a large ribosomal subunit, completing a translation initiation complex -proteins called initiation factors are required to bring all these componets together -the cell also spends energy in the form of a GTP molecule to form the initiation complex 5)At the completion of the initiation process, the initiator tRNA sits in the P site of the ribosome, and the vacant A site is ready for the next aminoacyl tRNA | |
| 669180913 | Elongation of Translation | -amino acids are added one by one to the preceding amino acid; each addition involves the participation of several proteins called elongation factors and occurs in a three step cycle: 1) Codon Recognition-The anticodon of an incoming aminoacyl tRNA base-pairs with the complementary mRNA codon in the A site. Hydrolysis of GTP increases the accuracy and effieciency of this step 2) Peptide Bond Formation. An rRNA molecule of the large subunit catalyzes the formation of a peptide bond between the new amino acid in the A site and the carboxyl end of the growing polypeptide in the P site. This step attaches the polypeptide to the tRNA in the A site. 3) Translocation the ribosome translocates the tRNA in the A site to the P site. The empty tRNA in the P site is moved to the E site, where it is released. The mRNA moves along with its bound tRNAs, bringing the next codon to be translated into the A site. | |
| 669970708 | Termination of Translation | 1)When a ribosome reaches a stop codon on mRNA, the A site of the ribosome accepts a protein called a release factor instead of tRNA 2) The release factor hydrolyzes the bond between the tRNA in the P site and the last amino acid of the polypeptide chain. The polypeptide is thus freed from the ribosome. 3) The two ribosomal subunits and the other components of the assembly dissociate. | |
| 669970709 | Release Factor | -a protein that binds directly to the stop codon on the A site during termination -causes the addition of a water molecule instead of an amino acid to the polypeptide chain | |
| 669970710 | Polyribosomes (or polysomes) | -an aggregation of several ribosomes attached to one messenger RNA molecule | |
| 669970711 | Post-translational Modifications | -amino acids may be chemically modified; one or more amino acids at the beginning of the chain may be enzymatically removed; segments of the polypeptide may be excised; or several polypeptides may associate into a quaternary structure | |
| 671031764 | Signal Peptide | -a stretch of amino acids on a polypeptide that targets the protein to a specific destination in a eukaryotic cell -a sequence of about 20 amino acids at or near the leading (amino) end of the polypeptide | |
| 671031765 | Signal-Recognition Particle (SRP) | -a protein-RNA complex that recognizes a signal peptide as it emerges from the ribosome | |
| 671031766 | SRP RNA | -a component of the signal-recognition particle (SRP), -the protein-RNA complex that recognizes the signal peptides of polypeptides targeted to the ER | |
| 671031767 | Small Nucleolar RNA (snoRNA) | -aids in processing of pre-rRNA transcripts for ribosome subunit formation in the nucleolus | |
| 671031768 | Small interfering RNA (siRNA) and microRNA (miRNA) | -are involved in regulation of gene expression | |
| 671031769 | Prokaryote Genes | -DNA in cytoplasm -circular chromosome -naked DNA -no introns | |
| 671031770 | Eukaryote Genes | -DNA in nucleus -linear chromosomes -DNA wound on histone proteins -introns vs. exons | |
| 671031771 | Translation in Prokaryotes | -transcription and translation are simultaneous in bacteria -DNA is in cytoplasm -no mRNA editing -ribosomes read mRNa as it is being transcribed | |
| 671031772 | Translation: Prokaryotes vs. Eukaryotes | -time and physical separation between processes-takes eukaryote about 1 hour from DNA to protein -no RNA processing | |
| 671031773 | Mutations | -changes in the genetic information of a cell (or virus), ultimately creating genetic diversity | |
| 671031774 | Point Mutations | -a change in a gene at a single nucleotide pair | |
| 671031775 | Base Pair Substitution | -a type of point mutation -the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides | |
| 671031776 | Missense | -the most common type of mutation -a base pair substitution in which the new codon makes sense in that it still codes for an amino acid | |
| 671031777 | Nonsense | -a mutation that changes an amino acid codon to one of three stop codons, resulting in a shorter and usually nonfunctional protein | |
| 671031778 | Insertion | -a mutation involving the addition of one or more nucleotide pairs to a gene | |
| 671031779 | Deletions | -a mutational loss of one or more nucleotide pairs from a gene | |
| 671031780 | Frameshift Mutation | -a mutation occurring when the umber of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the following nucleotides into codons | |
| 671031781 | Mutagen | -a chemical or physical agent such as X-rays and UV light that interacts with DNA and causes a mutation | |
| 671036676 | Spontaneous Mutations | -include base-pair substitutions, insertions, deletions, and longer mutations that occur during DNA replication, repair, or recombination |